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Tuesday, May 16, 2006 - 11:30 AM
APP24.4

Deposition of Nickel-Aluminide Coatings by Gaseous Detonation Spraying

Y. A. Kharlamov, GIK Institute of Engineering Sciences and Technology, Topi, Pakistan, Topi, Pakistan; M. Y. Kharlamov, Dalh East Ukrainian National University, Lugansk, Ukraine

The influence of sprayed particles velocity on formation of coatings from intermetallides is discussed. The results of experimental testing of nickel aluminide spraying possibilities by detonation methods are given. The ways of improving of technology of thermal spraying of  intermetallides are shown. The nickel-aluminide (Ni-Al) coatings are used for oxidation and corrosion resistance up to about 750 oC. Usually these coatings are obtained by plasma spraying, and little known about Ni-Al formation during detonation spraying. In this paper results of study of microstructure and character of boundary interaction between low-carbon steel substrate and coating are discussed. The 85% nickel - 15% aluminide powder with 40-100 mm sizes was used for spraying. For study of microstructure of coatings and substrate-coating interface the microrentgenoscopy analysis was used. The coatings have distinct layer structure. The certain content of iron was found into coating subsurface layer, which adjacent to substrate, during analysis of transverse section of coatings at FeKa characteristic radiation. The characteristic feature of aluminum distribution into coating is certain lamination. Nickel is distributed more uniformly, though also there is some layering. 
The primary phases of detonation sprayed NiAl powder coatings are nickel aluminides NiAl and Ni3Al, and solid solution of Ni into NiAl. The more well-defined layering of Al distribution is connected with oxidation of powder particles during their flight in impulse high temperature, high velocity jet of gaseous detonation products. During heating and melting of powder particles the film, which consist from aluminum oxides, is forming. This film is takes part in coating formation and affect on Al layering distribution. The other important reason is the presence of NiAl and Ni3Al phases in coating structure.
From analysis of distribution curves of elements radiation intensity it is evident that between coating and substrate the transition zone by thickness as 10-15 mm is forming. The character of distribution curves of Al and Ni is justify the lamination location of NiAl and Ni3Al phases into coating.

Summary: The influence of sprayed particles velocity on formation of coatings from intermetallides is discussed. The results of experimental testing of nickel aluminide spraying possibilities by detonation methods are given. The ways of improving of technology of thermal spraying of intermetallides are shown. For study of microstructure of coatings and substrate-coating interface the microrentgenoscopy analysis was used. The character of distribution curves of Al and Ni is justify the lamination location of NiAl and Ni3Al phases into coating.